Photographic defect recorder

ABSTRACT

A machine is disclosed herein for rapidly inspecting threads and/or yarns for defects, such as slubs, neps, doubles and/or knots, etc. The machine automatically counts the total number of yards of thread or yarn inspected, the total number of defects present in the inspected thread or yarn and makes a permanent record, such as a photograph of each and every defect.

United S t ates Patent [in entun Edwin R. Bridenbaugh;

Lawrence J Sherman, both of Huntsville. Ala.

App] M, 874,635

Filed Nov. 6, I969 Patented Aug. 10, l97l Asxignee Automation Industries, Inc.

Los Angeles, Calif.

PHOTOGRAPHIC DEFECT RECORDER IOClaims, 7 Drawing Figs.

US. Cl. v .i 346/33 F, 346/10"! R, 73/160, 95/12.)5/36, 356/200 lnt. L'l.v r. .7 (NM 9/42 Field of Search. 346/33 F 33 A.107R;ij/rnl refi o/iie DF, 219 s; 356/238,237, 200, 199;95/r I, r2 2 R, 36

[56] References Cited UNITED S'IATES PATENTS 1.947.729 2/1934 Morrison 95/[2 834,206 5/1958 Mindheim eta] r r 73/!59 3,l76 3()6 3/1965 Burns 346/33 Primary Examiner-Joseph W Hartary Ar!arney- Dan R. Sadler ABSTRACT: A machine is disclosed herein for rapidly inspecting threads and/0r yarns for defects, such as slubs. neps. doubles and/0r knots, etc, The machine automatically counts the total number ofyards of thread or yarn inspected, the total number ofdefects present in the inspected thread or yarn and makes a permanent record, such as every defect.

a photograph of each and H0 H8 [04% H6 no w r24 n2 j Strobe Incremental 92 Trigger hunlsn 94 I00 L vz r l ble 21-- Detect counr Counter 96 ea J I Amplifier ford 1 64 Counter PATENTEU AUG] 0 IQYI SHEET 1 OF 2 Flip Flop I I j 86 I04" I Strobe llncrernarptal I Trigger Mechomsm w 92 94 I00 ,1 9e K |2|- Detect Delay 00 i Counter er 96 I 68 l 69 [i1 AC j DC 42 r\ 4e 44 4e 3 5e r 50 52 5s o I 5O 70 Control a fmphfler 54 72 Yard 3 64 Counter 1 If!!! 11 II 11 1 111% r I 1 1 I I I c I 1 1 1 I I I I I :1

ATTORNEY.

PATENTED AUG] 015m 3599 2213 saw 2 [1F 2 Inspection ATTORNEY.

Edwin R. Bridenbaugh, ;9 Lawrence W. Shermcm, v INVENTORS.

PHOTOGRAPHIC DEFECT RECORDER BACKGROUND AND PRIOR ART Threads, yarns and similar materials are normally formed by twisting several smaller filaments together. A perfect" thread or yarn has a consistent quality, uniform diameter and no discontinuities over its entire length. However, during the manufacturing process various imperfections, such as slubs, neps, knots, doubles, etc., may occur. Defects of this nature interfere with the subsequent use of the yarn during such operations, as weaving, knitting, or sewing, etc.

Historically, such defects have been located and evaluated by an operator manually inspecting selected samples of the overall output of a machine. Such an inspection process does give an indication of the quality of the thread or yarn and assists to some degree in quality control operations. However, it is only a partial inspection of the entire product an has a very limited accuracy. Moreover, because of the human element the inspection is inherently not only slow but is also subject to possible error. 7

More recently it has been proposed to provide some sort of inspection equipment for mechanically and/or automatically inspecting threads, yarns, etc., at high rates of speed. Since the more defects common, such asslubs, neps, doubles, knots, etc., cause substantial increases in the diameter, the inspection equipment has normally been designed to detect any abnormal increases in diameter.

In one type of inspection equipment when when a defect is detected the thread or yarn is automatically cut and inspection process is stopped. The operator must then removed the imperfections and rejoin the free ends. It can be appreciated this is a relatively slow process and still requires an operator.

In another type of inspection equipment the thread or yarn is fed continuously therethrough without any interruptions. A counter is actuated each time a defect is detected whereby a count is accumulated of the total number of defects present. It has been found any given malfunctioning of the manufacturing equipment produces distinctive defects. Accordingly, if a skilled operator can observe the defect he can usually very quickly determine what portion of the manufacturing equipment is not functioning correctly and what steps are required to eliminate the trouble. Accordingly, although this type of equipment is capable of providing high-speed inspection and giving considerable valuable information as to the quality of the thread or yarn, it does not provide any significant information as to the nature or types of defects, and is, therefore, not entirely satisfactory from a quality control standpoint.

SUMMARY The present invention provides means for overcoming the foregoing difficulties. More particularly, the present invention provides means for automatically and continuously inspecting long lengths of thread or yarn and accumulating a total count of the number of defects present. In addition, a separate visual record is made of each individual defect whereby the operator can very'quickly and reliably evaluate the source of the defects.

In the limited number of embodiments of the invention disclosed herein, means are provided for continuously scanning the thread or yarn at a very high rate of speed and sensing any defects. Whenever a defect is detected in a thread or yarn a high-speed photograph is taken of a short segment containing the defect. The operator can then visually study the photograph to determine the nature of the defect and its source.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a combination diagrammatic cross-sectional view and block diagram of an inspection instrument embodying one form of the present invention;

FIG. 2 is a view of a record produced by the inspection instrument of FIG. 1;

FIG. 3 is a diagrammatic representationof a modification portion of the instrument of FIG. l;and

FIGS. 4 to 7, inclusive, are diag'rainm'atic representations similar to FIG. 3 but showing several additional modifications thereof.

DETAILED DESCRIPTION OF TI-IE DRAWINGS Referring to the drawings in more detail, the present invention is embodied in an inspection instrument 10 for continuously inspecting long lengths of thread orya'rn 12 at high rates of speed. The present instrument 10 may be used for identifying a wide variety of different types of defects. However, by way of example, it is particularly adapted to identify defects such as slubs 14, nebs 16, knots 18, doubles 20, etc.

The instrument 10 may be installed in a production line for inspecting thread or yarn 12 as it is being produced. However, in the present instance it is particularly adapted to inspect thread or yarn 12 after it has been produced and wound onto a bobbin or spool 22. p I

The instrument 10 includes a box or housing 24 for enclosing and protecting substantially all of the various parts and components thereof. A bracket 26 may be provided on the housing 24 for supporting one or more spools 22 containing thread or yarn 12 to be inspected.

A series of guides 28, 30, 32, 34, 36 and 38 are provided for stripping the thread 12 from the spool 22 and leading it through the instrument 10. The guides include a first pulley 28 for creating a spinning loop 38 around the spool 22, three pulleys 30, 32 and 34 for controlling the tension, an aperture 36 in the top of the housing 24 and a discharge opening 38 in the bottom of the housing 24. After the thread passes through the discharge opening 38, it may be fed to a suitable winding mechanism for rewinding onto a spool or to some other suitable utilizing means.

Although the thread 12 may be pulled through the instrument 10 by the utilizing means, etc., it has been found preferable to provide a drive 40 inside of the housing 10. The drive 40 is effective to transport the thread 12 through the housing 24 at a high rate of speed without creating excessive tensions, etc.

The drive 40 may be of a constant speed variety whereby the thread 12 will always travel through the housing 24 at a fixed speed. However, it has been found preferable to provide some form of control over the linear speed of the thread 12. This is especially true when the instrument 10 is to be used for inspecting an assortment of threads, yarns 12, etc., having diameters which vary over a substantial range. Also, by providing a variable speed it is possible to accelerate the thread 12 betweena dead standstill-and high speeds without breaking the thread 12.

The present drive 40 includes a drive drum 42 and idler drum 44. These drums 42 and 44 tightly mesh with each other and compress the thread 12 therebe'tween whereby the thread 12 cannot slip. The drive drum'42 is mounted ona rotating shaft 56. The shaft 56 is coupled to a drive motor 46 by a speed-reducing belt drive 48. This motor 46 is preferably a variable speed one, such as a series-wound AC motor.

A suitable speed control 50 is coupled to the motor 46 for regulating its speed. A knob 52 projects from the front panel 51 of the instrument I0 for adjusting the speed of the motor 46 and the rate at which the thread 12 is fed through the instrument l0.

A speed-reducing gear train 68 may be coupledto the shaft 56. The magnetic proximity switch 70 is positioned adjacent one of the gears whereby anelectrical signal will be produced each time a predetermined increment of thread 12 has been fed passed the drive wheel 44. This increment is considerably longer than the increment established in the speed control or tachometer wheel. By way of example, this increment may be equal to some unit suitable for'measuring the length of the thread 12, i.e., a yard.

A pulse will be produced by the proximity switch 70 each time a yard of thread 12 passes between the drive and idler wheels 42 and 44. A counter 72 is mounted on the front panel 51 of the instrument l and electrically coupled to the proximity switch 70. This counter 72 will accumulate a count of the total yards of thread inspected.

A tachometer disk 54 may be mounted on the shaft 56 so as to rotate with the drums 42 and 44 and the travel of the thread 12. An annular series of apertures 58 are spaced around the periphery of the disk 54. An electric light 50 and photoelectric pickup 62 are disposed on the opposite sides of the disk 54 in alignment with the apertures 58.

As a consequence, each time the drums 42 and 44 rotate and the thread 12 moves a predetermined distance, a flash of light will strike the photocell 62 and a pulse will be produced. By way of example, the increment of travel may be on the order of one-quarter inch whereby each electric pulse from the photocell indicates a thread movement of one-quarter inch.

The output of the photocell 62 is coupled to an amplifier 64. This amplifier 64 increases the amplitude of the tachometer pulses to a more useful level. It may also be effective to shape the pulses into a more desirable or standardized shape, such as a unipolar "wave with very short rise and fall times.

The output of the amplifier 64 may be coupled to an AC-to- DC frequency converter 66 or similar device for converting the pulses into a DC or slowly varying signal having an amplitude corresponding to the instantaneous frequency of the pulses. A suitable meter 68 may be mounted on the front panel 51 of the instrument and coupled to the output of the converter 66 so as to indicate the amplitude of the DC signal.

This meter 68 may be calibrated in units of speed whereby it will continuously indicate the instantaneous speed at which the thread 12 is traveling as determined by the setting of the control knob 52.

A search unit 74 is provided for scanning the thread 12 as it passes through the inspection instrument and detecting any defects that may be present. Although any type of defect may be detected, in the present instance the search unit 74 is especially effective in detecting defects which produce abnormal increases in the diameter of the thread 12.

The search unit 74 includes an arm or feeler 76 which slides or rides upon the thread 12 as it passes over the pulley 32. N ormally, the diameter of the thread 12 is substantially uniform and the feeler 76 will remain in a substantially static position. However, whenever a defect, such as a slub, nep, double and/or knot, etc., passes over the pulley 32 the diameter of the thread 12 will momentarily increase whereby the feeler 76 is momentarily deflected backwards away from the pulley 32.

An electrical contact is provided on the back side of the feeler 76 so as to be carried therewith. A second or mating contact 80 is mounted on a support so as to be in alignment with the first contact when the feeler 76 is deflected back by a defect. Normally the clearance between the contacts is just large enough to insure their remaining open when a thread 12 having the maximum acceptable diameter is present. If a defect increases the diameter beyond this amount the contacts will close.

The second contact 80 may be mounted upon a fixed support. However, it has been found desirable to make the contact 80 movable over at least a limited range whereby the clearance space between the contacts is adjustable. This is particularly true when the instrument 10 is to be employed for inspecting a wide variety of threads, yarns, etc., having a wide variety of diameters.

In the present embodiment the contact 80 is mounted on the end ofa thumbscrew 82. By manually adjusting thethumbscrew 82 the operator moves the contact 80 to adjust the,

clearance space. Normally the contact 80 may be movedin or out over a range of about one-fourth inch or even one-half inch depending upon the range of diameters to be inspected.

The contact 80 is connected to one input 88 of a bistable multivibrator or flip-flop 84. As long as the contact 80 remains open the flip-flop 84 will remain in one condition. More particularly, under these conditions the output 86 remains low or at ground level. As soon as the contact is'closed the flipflop 84 switches into its other condition (i.e., the output 86 becomes high or positive relative to ground). The flip-flop 84 remains in this condition until a signal is applied to the second input 90.

The output of the flip-flop 84 is in turn coupled to one input 94 of an AND gate 92. The opposite side 96 of the AND gate 92 is in turn coupled to the output of amplifier 64 so as to receive the tachometer pulses resulting from the rotation of the tachometer disk 54.

Since the contact is normally open the output 86 of the flipflop 84 is normally low. As a consequence the gate 92 is normally closed. Thus even though the tachometer pulses occur continuously on the input 96 they will not pass through the AND gate 92. However, whenever the output 86 of the flipflop 84 rises, the AND gate 92 will open and permit the tachometer pulses to pass therethrough.

The output of the AND gate 92 is coupled to a counter 98. The counter 98 is effective to accumulate a count of the tachometer pulses passed by the AND gate 92. When the gate 92 is closed no pulses will reach the counter 98 and no pulses will be accumulated. When the number of counted pulses reaches a predetermined level the counter 98 trips" and clears itself for accumulating a new count. At the same time it produces a signal on the output 100 and then a signal on the output 102. The signal on the first output 100 may precede the signal on the output 102 by a short interval.

The output 100 is coupled to the reset input of the flipflop 84. As a result when the counter 98 clears itself it will also cause the output 86 of the flip-flop 84 to return to ground whereby the AND gate 92 closes and prevents any further tachometer pulses reaching the counter 98.

The capacity of the counter 98 (i.e., the number of pulses it will accumulate before it trips" corresponds to the number of tachometer pulses which occur when the thread 12 travels a distance equal to the length of thread 12 between the feeler 76 and a checkpoint 104.

In other words, when an enlargement such as a defect 108 on the thread 12 closes the contact 80, the counter 98 will begin to accumulate a count and will continue to do so until the defect 108 reaches the checkpoint 104. Just as the defect 108 passes through the checkpoint 104 the counter 72 clears itself and produces a signal on the output 100. It is to be noted that checkpoint 104 is indicated as having an extended length. This length is a function of the distance represented by the tachometer pulses. Since the pulses occur on the order of each one-fourth inch of travel the checkpoint will have a length on this order.

The signal output is coupled to a suitable recorder for recording the nature of the defect. In the present instance the recorder includes a camera 106 which photographs the defects so as to make a permanent record thereof. A conventional camera may be used but it preferably has a fast-acting shutter capable of photographing the thread while it is movmg.

However, in the present instance the camera 106 includes a lighttight box 108 having openings 110 in the top and bottom for allowing the thread 12 and any enlargements thereon to travel freely therethrough. However, the openings 110 should be small enough to prevent any significant amount of light passing therethrough.

A film holder 112 is provided on one end of the box so as to be disposed on the front panel 51. A light plate 114 is provided for preventing exposure of the film while the film holder 112 is being loaded, etc., and/or the lighttight box 108 is opened, etc. Preferably the film in the holder 1 12 is of the selfdeveloping type such as employed in the so-called Polaroid Land Camera.

A lens 116 is disposed inside of the lighttight box 108 for projecting onto the film an image of the segment of thread 12 passing through the test point 104. The lens 116 which is situated in a lighttight partition 118 is mounted on a movable support. The support is operated by an incremental mechanism 120 and is adapted to incrementally move the lens 116 whereby the images of the thread 12 may be displaced slightly from each other.

As previously stated a conventional high-speed shutter may be employed in the camera 108. However, in this embodiment a strobe light 122 is disposed inside of the lighttight box 108 between the thread 12 and the lighttight partition 120. When the light plate 114 is removed and the film is uncovered there is normally not enough light to expose the film. When the light 122 flashes, a bright but short duration image of the imperfection 104 will be projected onto the film 126 and the counter 98 will be cleared.

The signal is coupled to the strobe light by means ofa strobe trigger 124. Each time the counter 98 accumulates the maximum count and clears itself, it produces a signal which causes the strobe trigger 124 to energize and flash the strobe light 122. This results in a very bright, short duration flash of light flooding the interior of the box 108. The light reflected from the thread 12 is focused by the lens 116 and projected onto the film. Because of the very bright and very short duration of the light a sharp, clear photographic image is formed on the film even though the thread may be traveling at a high rate of speed.

As previously stated the lens 116 is mounted on the partition 118 by means of a movable support. This support is connected to an incremental mechanism 120 which is coupled to the second output 102 of the counter 98. In the present instance this includes a mechanical drive which moves the lens 116 a small distance laterally each time a signal occurs on the output 102. Since this signal occurs immediately following the signal on the first output 100, immediately following each photograph the lens 116 will be moved slightly. As a consequence each exposure will be in the form ofa vertical image slightly displaced from the preceding exposure. This will result in a composite photograph 126 similar to FIG. 2. This photograph 126 contains a reproduction of each of the defects detected at any time during the scanning of the entire spool. if desired a defect counter 121 may be mounted on the front panel 51.

As an alternative any of the embodiments of FIG. 3 to 7 may be used for shifting the images. These include a mirror 128 or prism 130 which are twisted incrementally following each exposure. The camera 132 or the lens 134 may be shifted laterally or else the thread 12 may be shifted slightly.

In order to use the present invention for inspecting a thread 12, the spool 22 is mounted on the bracket 26 and the thread 12 is threaded through the guides. The drive 40 is then turned on to pull the thread 12 through the instrument 10. During the travel of the thread 12 if a defect lifts the feeler 76 the contact 80 closes and switchs the flip-flop 84. The resultant signal on the output 86 opens the gate 92 and allows the tachometer pulses to pass through the gate 92 to the counter 98. The counter 98 then accumulates a count and continues to do so until it reaches its capacity or desired count. It then clears itself, resets the flip-flop 84 and flashes the strobe 122. Following this it actuates the incremental mechanism 120.

After all of the thread 12 in the spool 22 is inspected the operator can develop the photograph 126 and study the various defects to determine the quality of the spool and/or the necessity for modifying the production process.

We claim:

1. An inspection apparatus for inspecting an elongated, continuous workpiece for defects, said apparatus including the combination of pickup means for scanning said workpiece, said pickup means being effective to sense defects in said workpiece, photographic means for recording a photographic image of the portions ofthe workpiece, and control means coupled to the pickup means for actuating the photographic means in response to the defects whereby the photographic image includes the portion of the workpiece containing said defects, said control means being effective to actuate said photographic means for making multiple exposures of said workpiece with each of said exposures being displaced from the preceding exposure. 2. An apparatus for continuously inspecting an elongated filament, said apparatus including the combination of means for continuously feeding said filament through a pickup zone and then an inspection zone, means in said pickup zone for scanning said filament as it passes through said zone for detecting defects therein, means for photographing the portion of said filament in the inspection zone, control means-coupled to said first and second means, said control means being responsive to the passage of the defeet for actuating the second means for making a photographic exposure of the filament each time a defect is detected, said control means being effective to make multiple exposures of said filament, and means effective to move the successive exposures relative to the preceding exposure. 3. The apparatus of claim 2 wherein the pickup zone and the inspection zone are separated from each other by a determined length of said filament, and said control means includes a delay for actuating the second means when the detected defect reaches the inspection zone. 4. An inspection apparatus for continuously inspecting an elongated thread including the combination of means for continuously feeding said thread through said apparatus, pickup means for scanning said thread at a pickup'zone to detect enlargements in said thread, camera means for photographing said thread at an inspection zone displaced at a predetermined distance from the pickup zone, control means coupled to the pickup means and to said camera means, said control means being effective to actuate the camera means each time a defect passes through the pickup means, time delay means in said control means, said time delay means being effective to actuate the camera means each time a defect passes through the pickup means, time delay means in said control means, said time delay means being effective to actuate said camera means a predetermined time interval after the detection of a defeet, said time delay being equal to the time required for the thread to travel from the pickup zone to the inspection zone, and indexing means in said control means, said indexing means being effective to cause each exposure of said thread to be displaced from the preceding exposure by a predeten mined amount whereby a single photograph is produced wherein images of all the defects are disposed parallel to each other. 5. The inspection apparatus of claim 4 wherein the timedelay means includes a tachometer pulse generator, said generator being effective to produce a pulse each time the thread moves a predetermined distance, means for counting said pulses, and means for activating said camera after that number of counted pulses corresponds to said distance between the two zones. 6. The inspection apparatus of claim 4 wherein said camera means includes a strobe light which is coupled to the time-delay means and is effective to produce a short duration burst of light while the defect is passing through the inspection zone. 7. An inspection apparatus for inspecting thread including the combination of means for feeding the thread through said apparatus at a substantially constant speed,

a tachometer in said feed means effective to produce a series of tachometer pulses representing predetermined increments of travel of the thread,

a pickup for riding on the thread and detecting any enlargements in said thread and producing a corresponding signal,

a pulse counter coupled to said detector and effective to commence accumulating a count of tachometer pulses whenever said pickup detects an enlargement in the thread,

a camera for photographing said thread,

said counter being effective to actuate said camera when the accumulated count of said pulses corresponds to the distance traveled by said thread as it moves from the pickup and into the field of view of the camera.

8. An inspection apparatus for continuously inspecting an elongated thread including the combination of:

means for continuously feeding said thread through said apparatus;

pickup means for scanning said thread at a pickup zone to detect enlargements in said thread;

camera means for photographing said thread at an inspection zone displaced at a predetermined distance from the pickup zone;

control means coupled to said pickup means and to said camera means, said control means being effective to actuate the camera means each time a defect passes through the pickup means; and

time-delay means in said control means, said time-delay means being effective to actuate said camera means a predetermined time interval after the detection of a defeet, said time delay being equal to the time required for a thread to travel from the pickup zone to the inspection zone, said time delay means including a tachometer pulse generator, said generator being effective to produce a pulse each time the threads move a predetermined distance, means for counting said pulses, and means for actuating said camera after the number of counted pulses corresponds to said distance between the two zones.

9. The inspection apparatus as defined in claim 8 wherein said camera means including a strobe light which is coupled to the time-delay means and being effective to produce a short burst of light while the defect is passing through the inspection zone.

10. An inspection apparatus for continuously inspecting an elongated thread including the combination of:

means for continuously feeding said thread through said apparatus;

pickup means for scanning said thread at a pickup zone to detect enlargement is said thread;

camera means for photographing said thread at an inspection zone displaced at a predetermined distance from the pickup zone;

control means being coupled to said pickup means and to said camera means, said control means being effective to actuate the camera means each time a defect passes through the pickup means; and

time-delay means in said control means, said time-delay means being effective to actuate said camera means a predetermined time interval after the detection of a defect, said time-delay means being equal to the time required for the thread to travel from the pickup zone to the inspection zone;

said camera means including a strobe light which is coupled to the time-delay means and being effective to produce a short burst of light while the defect is passing through the inspection zone. 

1. An inspection apparatus for inspecting an elongated, continuous workpiece for defects, said apparatus including the combination of pickup means for scanning said workpiece, said pickup means being effective to sense defects in said workpiece, photographic means for recording a photographic image of the portions of the workpiece, and control means coupled to the pickup means for actuating the photographic means in response to the defects whereby the photographic image includes the portion of the workpiece containing said defects, said control means being effective to actuate said photographic means for making multiple exposures of said workpiece with each of said exposures being displaced from the preceding exposure.
 2. An apparatus for continuously inspecting an elongated filament, said apparatus including the combination of means for continuously feeding said filament through a pickup zone and then an inspection zone, means in said pickup zone for scanning said filament as it passes through said zone for detecting defects therein, means for photographing the portion of said filament in the inspection zone, control means coupled to said first and second means, said control means being responsive to the passage of the defect for actuating the second means for making a photographic exposure of the filament each time a defect is detected, said control means being effective to make multiple exposures of said filament, and means effective to move the successive exposures relative to the preceding exposure.
 3. The apparatus of claim 2 wherein the pickup zone and the inspection zone are separated from each other by a determined length of said filament, and said control means includes a delay for actuating the second means when the detected defect reaches the inspection zone.
 4. An inspection apparatus for continuously inspecting an elongated thread including the combination of means for continuously feeding said thread through said apparatus, pickup means for scanning said thread at a pickup zone to detect enlargements in said thread, camera means for photographing said thread at an inspection zone displaced at a predetermined distance from the pickup zone, control means coupled to the pickup means and to said camera means, said control means being effective to actuate the camera means each time a defect passes through the pickup means, time delay means in said control means, said time delay means being effective to actuate said camera means a predetermined time interval after the detection of a defect, said time delay being equal to the time required for the thread to travel from the pickup zone to the inspection zone, and indexing means in said control means, said indexing means being effective to cause each exposure of said thread to be displaced from the preceding exposure by a predetermined amount whereby a single photograph is produced wherein images of all the defects are disposed parallel to each other.
 5. The inspection apparatus of claim 4 wherein the time-delay means includes a tachometer pulse generator, said generator being effective to produce a pulse each time the thread moves a predetermined distance, means for counting said pulses, and meaNs for activating said camera after the number of counted pulses corresponds to said distance between the two zones.
 6. The inspection apparatus of claim 4 wherein said camera means includes a strobe light which is coupled to the time-delay means and is effective to produce a short duration burst of light while the defect is passing through the inspection zone.
 7. An inspection apparatus for inspecting thread including the combination of means for feeding the thread through said apparatus at a substantially constant speed, a tachometer in said feed means effective to produce a series of tachometer pulses representing predetermined increments of travel of the thread, a pickup for riding on the thread and detecting any enlargements in said thread and producing a corresponding signal, a pulse counter coupled to said detector and effective to commence accumulating a count of tachometer pulses whenever said pickup detects an enlargement in the thread, a camera for photographing said thread, said counter being effective to actuate said camera when the accumulated count of said pulses corresponds to the distance traveled by said thread as it moves from the pickup and into the field of view of the camera.
 8. An inspection apparatus for continuously inspecting an elongated thread including the combination of: means for continuously feeding said thread through said apparatus; pickup means for scanning said thread at a pickup zone to detect enlargements in said thread; camera means for photographing said thread at an inspection zone displaced at a predetermined distance from the pickup zone; control means coupled to said pickup means and to said camera means, said control means being effective to actuate the camera means each time a defect passes through the pickup means; and time-delay means in said control means, said time-delay means being effective to actuate said camera means a predetermined time interval after the detection of a defect, said time delay being equal to the time required for a thread to travel from the pickup zone to the inspection zone, said time delay means including a tachometer pulse generator, said generator being effective to produce a pulse each time the threads move a predetermined distance, means for counting said pulses, and means for actuating said camera after the number of counted pulses corresponds to said distance between the two zones.
 9. The inspection apparatus as defined in claim 8 wherein said camera means including a strobe light which is coupled to the time-delay means and being effective to produce a short burst of light while the defect is passing through the inspection zone.
 10. An inspection apparatus for continuously inspecting an elongated thread including the combination of: means for continuously feeding said thread through said apparatus; pickup means for scanning said thread at a pickup zone to detect enlargement is said thread; camera means for photographing said thread at an inspection zone displaced at a predetermined distance from the pickup zone; control means being coupled to said pickup means and to said camera means, said control means being effective to actuate the camera means each time a defect passes through the pickup means; and time-delay means in said control means, said time-delay means being effective to actuate said camera means a predetermined time interval after the detection of a defect, said time-delay means being equal to the time required for the thread to travel from the pickup zone to the inspection zone; said camera means including a strobe light which is coupled to the time-delay means and being effective to produce a short burst of light while the defect is passing through the inspection zone. 